Prosthetic limbs are attached to a residual limb or stump of an amputee by a stump socket, which is a shell that closely conforms to the residual limb. For example, a knee prosthetic includes a stump socket that is attached to the stump of an amputee. The stump socket has a threaded socket adaptor which is adapted to engage with an intermediate connector, such a pyramid plug. The pyramid plug then connects the socket adaptor to an upper tube clamp. A lower tube clamp is connected to the upper tube clamp with a tube. The lower tube clamp is then connected to a prosthetic foot with a connector.